Glycolipid Presentation by CD1

Abstract CD1 molecules constitute a family of nonpolymorphic, MHC class I‐like antigen‐presenting glycoproteins, which bind amphipathic lipid antigens and present them to T cells. These proteins are involved in presenting a broad range of self and foreign lipid antigens to variable T lymphocytes and natural killer T cells bearing a semi‐invariant T‐cell receptor ( iNKT ). It has become clear that the recognition of lipid antigens by T cells plays an important role in the detection and clearance of pathogens, immune response regulation and tissue surveillance. Key Concepts Self and microbial lipids and glycolipids are recognised by T cells. Hydrophobic pockets of CD1 proteins allow lipid antigens to be loaded via their alkyl chains, while the hydrophilic part of the antigen is presented to T‐cell receptors. CD1 proteins are non‐polymorphic and predominantly expressed on the surface of antigen‐presenting cells. Glycolipids can be processed into smaller antigenic structures in the endosomal pathway. CD1e, a soluble protein found in late endosomes, assists in lipid antigen editing and loading onto other CD1 proteins. CD1‐restricted T cells express αβ or γδ TCR and are found in CD4 + , CD8 + or double‐negative T‐cell populations. The frequency of autoreactive T cells is high among CD1‐restricted T cells.